Fabrication of single crystalline bulk GaN substrates using GaAs as seed crystals

半导体β-FeSi_2作为一种在Si衬底上制备光电器件的新型材料，受到了广泛的关注。本工作的目的是在Si（001）衬底上获得高质量的β-FeSi_2薄膜，并在此基础上制备可用作光互连光源的发光二极管。本项目取得的主要成果如下：1.以外延生长的β-FeSi_2为模板和SiO_2覆盖层，在Si（001）衬底上沉积纳米Si/Fe多层膜，经退火处理后得到了高质量的β-FeSi_2薄膜。SiO_2覆盖层阻止了β-FeSi_2的热团聚。β-FeSi_2薄膜的导电类型由沉积的β-FeSi_2的Si/Fe比控制。p型和n型p-FeSi_2薄膜的最大电子和空穴迁移率分别为6900 cm ^2/ Vs和13000 cm ^2/Vs。这是有史以来最高的价值。2.采用反应沉积外延法生长β-FeSi_2，并利用分子束外延（MBE）技术将其嵌入Si中，首次在Si p-n二极管中实现了1.6μm的室温电致发光。当注入电流密度大于10A/cm ^2时，在室温下观察到1.6μm的电致发光。这种电致发光的实现是由于在500℃的较低温度下，用合适的氧浓度较低的Si衬底将β-FeSi_2包埋在分子束外延硅中。

Semiconducting β-FeSi_2 has been attracting much attention as a promising material for opto-electronic devices on Si substrates. Purpose of this work is to obtaine high quality β-FeSi_2 films on Si (001) substrates and furthermore to fabricate light-emitting diodes which can be used as light sources in optical inter-connections. Achievements in this project are as follows.1. [100]-oriented high quality β-FeSi_2 films were obtained.The β-FeSi_2 films were fabricated by annealing nanometer-thick Si/Fe multilayers deposited on a Si (001) substrate using epitaxial β-FeSi_2 as a template and a SiO_2 capping layer. The SiO_2 capping layer prevented aggregation of β-FeSi_2 against heating. The conduction type of the β-FeSi_2 films was controlled by deposited Si/Fe ratios of the β-FeSi_2. The maximu electron and hole mobilitis were 6900cm^2/ Vs and 13000cm^2/Vs at about 50 K, for the p-type and n-type p-FeSi_2 films, respectively. These are the highest values ever reported.2. Room temperature 1.6μm electroluminescence was realized from a Si p-n diode with β-FeSi_2 active region for the first time.The β-FeSi_2 was grown by reactive deposition epitaxy, and embedded in Si by molecular beam epitaxy (MBE). The 1.6μm electroluminescence (EL) was observed at RT for injected current density above 10A/cm^2. Realization of this EL was attributed to embedding β-FeSi_2 by MBE-Si at relatively low temperature of 500℃, and using suitable Si substrates with small oxygen concentrations.